User blog comment:CharlesW9 - ROBLOX/Unavailable Pokémon (136)/@comment-31267872-20171016204656

Bruxish: Fishing in Lost Islands - Mini Beach

Drampa - Air Quest / Soaring (once it comes out)

Dhelmise: Near anchor on Abandoned Ship (off the shore of Mini-Beach) after clearing through the boat

Jangmo-o: (Very Rare) Lost Islands - Mountain Peaks

Hakamo-o: Level 35 Jangmo-o

Kommo-o: Level 45 Hakamo-o

The 4 Tapus: Create the locations yourself, probably just have them in like a cave or chamber or I dunno xD

Cosmog: Ultra Space

Cosmoem: Level 43 Cosmog

Solgaleo/Lunala: Level 53 Cosmoem, day/night respectively

The Ultra Beasts (#793 Nihilego - #799 Guzzlord): Ultra Space

Necrozma: Somewhere underground, asleep

Magearna: Some... Steel Chamber or factory..? dunno